HALL Current Sensor DAQ 8-Layer Stackable HAT for Raspberry Pi

FEATURES

• Each input can read HALL Current Sensors from 1A to 300A
• Supports 2.5±0.625V and 2.5V±1V AC/DC HALL Sensors
• Eight Level Stackable
• Pluggable Connectors 26-16 AWG wires
• Eight software programmable LEDs
• RS485/MODBUS Port
• 5VDC Power Supply powers also the Raspberry Pi
• 24V Power Supply provides up to 5A to Raspberry Pi
• Real Time Clock with Battery Backup
• On board hardware watchdog
• Resettable fuse
• TVS protection on all inputs
• 32-bit Processor running at 64MHz
• Uses only I2C port (address 0x58 to 0x5f), leaves all GPIO pins available
• Works with any Raspberry Pi from ZERO to 5
• ECCN Code EAR99
  
• Command line
• Python Library
• Node-Red nodes
• Arduino Library
• Home Assistant Integration
• All mounting hardware included: stand-offs, screws and nuts
• Open source hardware

DESCRIPTION

Brings to Raspberry Pi eight channel data acquisition from HALL current sensors. Each input signal is processed with rail to rail instrumentation amplifiers with 30µV offset, 20pA bias and 0.01µV/°C drift. 

Can be used with HALL sensors from 1A to 300A, AC or DC, with 2.5±0.625V or 2.5V±1V outputs.

Eight LEDs can be programmed to trigger at a pre-set level of the analog inputs.

The Real Time clock will keep the time almost indefinitely during power failure using a CR2032 battery backup.

The hardware watchdog will monitor and power cycle the Raspberry Pi in case of software lockup. TVS diodes on all inputs protect the card for external ESD, and the on-board resettable fuse protects is from accidental shorts.

COMMUNICATION

Connect the HALL Current Sensor HAT to other Industrial Automation systems using RS485/Modbus communication ports. The RS485 can be driven either from the local processor implementing Modbus RTU device, or directly from the Raspberry Pi using the dedicated pins on the GPIO connector, which are routed to the RS485 driver. In and out connectors simplify daisy-chain wiring to other devices.

COMPATIBILITY

The HALL Current Sensor DAQ HAT share the I2C bus using only two of the Raspberry Pi’s GPIO pins to manage all eight cards. This feature leaves the remaining 24 GPIOs available for the user. The card is compatible with all Raspberry Pi versions from Zero to 5.

POWER REQUIREMENTS

The HALL Current Sensor DAQ HAT operates either with a 5V/5A, or 24V/1V external power supply. The HAT supplies 5V and up to 5A to Raspberry Pi on the GPIO bus. A local 3.3V regulator powers the rest of the circuitry. The card needs only 50mA to operate.

PLUGGABLE CONNECTORS

All the IO's are connected to heavy duty (8A), 3.5mm pitch pluggable connectors which make field wiring very convenient for installation and debugging.

CARD LAYOUT

• Power supply: 3.5mm Pluggable Connector, 5V/5A or 24V/1A
• Power consumption: 50mA
• On board resettable fuse: 7A
• HALL Sensor Inputs: 2.5±0.625V and 2.5V±1V AC/DC

MECHANICAL SPECIFICATIONS

DOWNLOADS

• Command line
• Schematic V1.0
• 3D Printing Enclosure
• 3D Step Model

SOFTWARE

SOFTWARE INTERFACES

You can write your own application using the Command Line or Python Libraries. No programming is required if you use the Node-Red nodes provided. You can drag-and-drop the functional blocks to design your application. Examples are provided at GitHub. 

FIELD CALIBRATION

All the analog inputs are calibrated at the factory, but firmware commands permit the user to re-calibrate the board, or to calibrate it to better precision. All inputs can be calibrated in two points; select the two points as close to possible to the two ends of scale. To calibrate the inputs, the user must provide analog signals. (Example: to calibrate 0-10V inputs, the user must provide a 10V adjustable power supply). Calibration process can be done using the command line interface provided.

WATCHDOG

The card contains a built-in hardware watchdog which will guarantee that your mission-critical project will recover and continue running even if Raspberry Pi software hangs up. After power up the watchdog is disabled, and becomes active after it receives the first reset or first period set.

The default timeout is 120 seconds. Once activated, if it does not receive a subsequent reset from Raspberry Pi within 2 minutes, the watchdog cuts the power and restores it after 10 seconds.

Raspberry Pi needs to issue a reset command on the I2C port before the timer on the watchdog expires. The timer period after power up and the active timer period can be set from the command line. The number of resets is stored in flash and can be accessed or cleared from the command line. All the watchdog commands are described by the online help function.

RS485/MODBUS Communication

The Sixteen Analog-Digital Inputs card contains a standard RS485 transceiver which can be accessed by the local processor or by Raspberry Pi. The desired configuration is set from three bypass DIP-switches marked TX and RX.

RS-485 Selection

If DIP-switches are ON, Raspberry Pi can communicate with any device with an RS485 interface. In this configuration the card is a passive bridge which implements only the hardware levels required by the RS485 protocol. To use this configuration, you need to tell the local processor to release control of the RS485 bus:

~$ 16univin [0]  cfg485wr 0 0 0 0 0

If DIP-Switches are OFF, the card can operates as MODBUS slave and implements the MODBUS RTU protocol. Any MODBUS master can access all the card's inputs, and set all the outputs using standard MODBUS commands. A detailed list of commands implemented and parameters addresses can be found on GitHub:

In both configurations the local processor needs to be programmed to release (DIP-switches ON) or control (DIP-switches OFF) the RS485 signals. See the command line online help for further information.

FIRMWARE UPDATE

The card firmware can be updated in the field by running a command. The update is made with the latest firmware version located on our servers. More instructions about the process can be found on GitHub. Please make sure there is no process, like Node-Red or Python scripts, that tries to access the card during the update process.

ACCESSORIES

DIN-RAIL MOUNTING

The card can be installed parallel on a DIN-Rail using the DIN-Rail Kit Type 1, or perpendicular using the DIN-Rail Kit Type 2.

SMART FAN

The Smart Fan provides a stackable cooling solution for Raspberry Pi. Its on-board processor powers the fan just enough to maintain the preset temperature of the Pi.

YOUR KIT

When you purchase the card you will receive the following items:

1. Sixteen Analog-Digital Inputs Card

2. Mounting hardware

• Four M2.5x18mm male-female brass standoffs
• Four M2.5x5mm brass screws
• Four M2.5 brass nuts

4. All required connector plugs

QUICK START

1. Plug your card on top of your Raspberry Pi and power up the system
2. Enable I2C communication on Raspberry Pi using raspi-config.
3. Install the software from github.com:

• • git clone https://github.com/SequentMicrosystems/8crt-rpi.git
    cd 8crt-rpi/
    sudo make install
    8crt

The program will respond with a list of available commands.